Bonded structure, sealed structure, electronic component including the same, bonding method, and sealing method

ABSTRACT

Provided are a bonded structure, a sealed structure, an electronic component including the same, a bonding method, and a sealing method, the bonded structure and sealed structure allow hermetic adhesion using an adhesive even when the materials of the bonding surfaces are different, or the bonding surfaces have low wettability for the adhesive. A sealed structure  21  used for an electronic component or the like includes a first bonding surface  17  on a first adherent  11  bonded to a second bonding surface  18  on a second adherent  16  via an adhesive layer  24 , the first and/or second bonding surfaces  17  and  18  having films  22  and  23  of film-forming compounds, the film-forming compounds being bound to the surfaces  17  and  18  at one end of the molecule thereof, and bound to a molecule of the adhesive at the functional group at the other end of the molecule.

TECHNICAL FIELD

The present invention relates to a bonded structure, a sealed structure,an electronic component including the same, a bonding method, and asealing method.

BACKGROUND ART

It is a well known technique to bond together a pair of opposed bondingsurfaces using an adhesive such as an instantaneous, photocurable, orhot melt adhesive. An adhesive is applied onto one or both of thebonding surfaces, and the adhesive wetting the surfaces is cured therebyprogressing adhesion between the pressure-bonded surfaces.

Wettability of the bonding surfaces for an adhesive depends on thechemical properties (for example, hydrophilicity, hydrophobicity, andsurface energy) of the bonding surfaces and the adhesive. Therefore, ifthe materials of bonding surfaces are different or the bonding surfacesare composed of fluorocarbon materials, the bonding surfaces haveinsufficient wettability for an adhesive. Accordingly, in such cases, itis difficult to achieve hermetic adhesion using an adhesive.

Electronic components such as semiconductor devices, image sensors, linesensors, liquid crystal displays (LCDs), plasma display panels (PDPs),and electroluminescence (EL) displays must be sealed in packages toprevent degradation by penetration of water. These electronic componentsrequires bonding of surfaces composed of different materials. Asdescribed above, in such cases, sufficient hermeticity cannot beachieved with an adhesive, so that a welding method (for example, seePatent Document 1), a solder sealing method (for example, see PatentDocument 2), or a low melting point glass sealing method (for example,see Patent Document 3) is used.

-   Patent Document 1: Japanese Unexamined Patent Application    Publication No. 5-174733-   Patent Document 2: Japanese Unexamined Patent Application    Publication (Translation of PCT Application) No. 2005-534048-   Patent Document 3: Japanese Unexamined Patent Application    Publication No. 2007-13026

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, the welding method, solder sealing method, and low meltingpoint glass sealing method require high temperatures for adhesion andsealing, which increases the production cost and causes problems such asthermal deformation of the bonding surfaces and degradation of theadherents. In addition, these methods are poorly applicable to bondingsurfaces composed of resin materials.

The present invention has been accomplished in view of theabove-described problems, and is intended to provide a bonded structure,a sealed structure, an electronic component including the same, abonding method, and a sealing method, thereby achieving hermeticadhesion with an adhesive even if the materials of both of the bondingsurfaces are different, or the bonding surfaces have low wettability forthe adhesive.

Means for Solving the Problem

A bonded structure for achieving the above-described object according toa first aspect of the present invention is a bonded structure includinga first bonding surface on a first adherent bonded to a second bondingsurface on a second adherent via an adhesive layer, the first and/orsecond bonding surfaces having a film of a film-forming compound, thefilm-forming compound being bound to the surface at one end of themolecule thereof, and bound to a molecule of the adhesive via afunctional group at the other end of the molecule.

A sealed structure according to a second aspect of the present inventionis a sealed structure including a first bonding surface on a firstadherent hermetically bonded to a second bonding surface on a secondadherent via an adhesive layer, the first and/or second bonding surfaceshaving a film of a film-forming compound, the film-forming compoundbeing bound to the surface at one end of the molecule thereof, and boundto a molecule of the adhesive via a functional group at the other end ofthe molecule.

In the sealed structure according to the second aspect of the presentinvention, the first and/or second adherents may be metal, ceramic,glass, or plastic.

In the sealed structure according to the second aspect of the presentinvention, the film of the film-forming compound is preferably amonomolecular film.

An electronic component according to a third aspect of the presentinvention includes the sealed structure according to the second aspectof the present invention. The electronic component according to thethird aspect of the present invention may be a semiconductor device, animage sensor, a line sensor, a liquid crystal display (LCD), a plasmadisplay panel (PDP), or an electroluminescence (EL) display sealed in apackage.

A bonding method according to a fourth aspect of the present inventionincludes: step A of bringing a first film-forming compound having ateach end of the molecule thereof a first functional group that forms abond with a molecule of an adhesive and a first surface bonding groupinto contact with a first bonding surface of a first adherent therebybinding the first surface bonding group to the surface functional groupof the first bonding surface to form a film of the first film-formingcompound on the first bonding surface; step B of bringing a secondfilm-forming compound having at each end of the molecule thereof asecond functional group for forming a bond with a molecule of theadhesive and a second surface bonding group into contact with a secondbonding surface of a second adherent to thereby binding the secondsurface bonding group to the surface functional group of the secondbonding surface to form a film of the second film-forming compound onthe second bonding surface; and step C of bringing the first bondingsurface having a film of the first film-forming compound into contact bypressure with the second bonding surface having a film of the secondfilm-forming compound while setting the adhesive to be in contact withthe first and second functional groups, thereby binding the first andsecond functional groups to the molecule of the adhesive.

A sealing method according to a fifth aspect of the present inventionincludes: step A of bringing a first film-forming compound having ateach end of the molecule thereof a first functional group that forms abond with the molecule of an adhesive and a first surface bonding groupinto contact with a first bonding surface on the edge of the firstadherent thereby binding the first surface bonding group to the surfacefunctional group of the first bonding surface to selectively form a filmof the first film-forming compound on the first bonding surface; step Bof bringing a second film-forming compound having at each end of themolecule thereof a second functional group that forms a bond with themolecule of the adhesive and a second surface bonding group into contactwith contacting a second bonding surface on the edge of a secondadherent thereby binding the second surface bonding group to the surfacefunctional group of the second bonding surface to selectively form afilm of the second film-forming compound on the second bonding surface;and step C of bringing the first bonding surface having a film of thefirst film-forming compound into contact by pressure with the secondbonding surface having a film of the second film-forming compound whilesetting the adhesive to be in contact with the first and secondfunctional groups, thereby binding the first and second functionalgroups to the molecule of the adhesive.

In the sealing method according to the fifth aspect of the presentinvention, the first and second functional groups may be amino groups orimino groups, and the molecule of the adhesive may have an epoxy group.

In the sealing method according to the fifth aspect of the presentinvention, the first and second surface bonding groups may bealkoxysilyl groups.

In the step C of the sealing method according to the fifth aspect of thepresent invention, the temperature of the first or second adherenthaving a higher coefficient of linear expansion is preferably lower thanthe temperature of the other adherent having a lower coefficient oflinear expansion.

In the sealing method according to the fifth aspect of the presentinvention, it is preferable that both of the films of the first andsecond film-forming compounds be monomolecular films.

Advantageous Effect of the Invention

In the bonded structure according to the first aspect of the presentinvention, the functional group of the film-forming compound bound tothe bonding surface is bound to the molecule of the adhesive therebyachieving high bonding strength regardless of the wettability of thebonding surface for an adhesive. As a result of this, higher adhesivestrength is achieved even if both of the bonding surfaces are differentin wettability for the adhesive, or have insufficient wettability forthe adhesive.

In the sealed structure according to the second to fourth aspects of thepresent invention, the functional group of the film-forming compoundbound to the bonding surface is bound to the molecule of the adhesivethereby securing high bonding strength and hermeticity regardless of thewettability of the bonding surface for the adhesive. As a result ofthis, sealing is achieved with high strength and higher reliability evenif both of the bonding surfaces are different in wettability for theadhesive, or have insufficient wettability for the adhesive.

In the sealed structure according to the third aspect of the presentinvention, the first and/or second adherents are metal, ceramic, glass,or plastic thereby favorably producing a sealed body with highhermeticity.

In the sealed structure according to the fourth aspect of the presentinvention, the film of the film-forming compound is a monomolecular filmthereby achieving excellent strength and reliability.

The electronic component according to the fifth and sixth aspect of thepresent invention includes the sealed structure according to the secondto fourth aspects of the present invention, whereby the electriccomponent is produced at a low cost, resists degradation by penetrationof moisture, and has excellent reliability.

In a bonding method according to a seventh aspect of the presentinvention, firstly, a film of the film-forming compound bound to thebonding surface is formed, and then the first and second functionalgroups of the film-forming compound are bound to the molecule of theadhesive thereby securing high bonding strength regardless of thewettability of the bonding surface for the adhesive. As a result ofthis, higher adhesive strength is achieved even if both of the bondingsurfaces are different in wettability for the adhesive, or haveinsufficient wettability for the adhesive.

In sealing methods according to eighth to twelfth aspects of the presentinvention, firstly, a film of the film-forming compound bound to thebonding surface is formed, and then the first and second functionalgroups of the film-forming compound are bound to the molecule of theadhesive thereby securing high bonding strength and hermeticityregardless of the wettability of the bonding surface for the adhesive.As a result of this, sealing is achieved with high strength and higherreliability even if both of the bonding surfaces are different inwettability for the adhesive, or have insufficient wettability for theadhesive.

In the sealing method according to the ninth aspect of the presentinvention, the first and second functional groups are amino groups orimino groups, and the molecule of the adhesive contains an epoxy group,whereby sealing is achieved with high peel resistance and highhermeticity.

In the sealing method according to the twelfth aspect of the presentinvention, the first and second surface bonding groups are alkoxysilylgroups, whereby sealing is achieved with high peel resistance and highhermeticity.

In the step C of the sealing method according to the eleventh aspect ofthe present invention, the temperature of the first or second adherenthaving a higher coefficient of linear expansion is lower than thetemperature of the other adherent having a lower coefficient of linearexpansion, whereby the occurrence of distortion due to the difference ofthe coefficients of linear expansion of the bonding surfaces isprevented, and sealing is achieved with high peel resistance and highhermeticity during practical use.

In the sealing method according to the twelfth aspect of the presentinvention, both of the films of the first and second film-formingcompounds are monomolecular films, whereby the number of chemical bondsbound to the molecule of the adhesive is large, and sealing is achievedwith high peel resistance and high hermeticity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory drawing schematically showing a section of animage sensor having the sealed structure according to one embodiment ofthe present invention.

FIG. 2 is a schematic diagram enlarged to a molecular level showing thesealed structure of the image sensor.

FIG. 3 is a schematic diagram enlarged to a molecular level illustratingthe step of forming a monomolecular film of the first film-formingcompound on the first bonding surface of a ceramic package, wherein (A)shows a cross section structure of the ceramic package before reaction,and (B) shows a cross section structure of the ceramic package havingthe monomolecular film of the first film-forming compound.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention are described below withreference to the accompanied drawings for a better understanding of thepresent invention.

FIG. 1 is an explanatory drawing schematically showing a section of animage sensor having the sealed structure according to one embodiment ofthe present invention, FIG. 2 is a schematic diagram enlarged to amolecular level showing the sealed structure of the image sensor, andFIG. 3 is a schematic diagram enlarged to a molecular level illustratingthe step of forming a monomolecular film of the first film-formingcompound on the first bonding surface of a ceramic package, wherein FIG.3(A) shows a cross section structure of the ceramic package beforereaction, and FIG. 3(B) shows a cross section structure of the ceramicpackage having the monomolecular film of the first film-formingcompound.

As shown in FIG. 1, an image sensor (an example of the electroniccomponent) including a sealed structure 21 according to one embodimentof the present invention has a sensor chip 12 mounted on a ceramicpackage (an example of the first adherent) 11. The ceramic package 11 isprovided with leads 13. The leads 13 are electrically connected toelectrode pads 14 for electrically connecting the sensor chip 12 to theexternal circuit via electrically conductive wires 15.

The image sensor 10 has a transparent window plate glass 16 (an exampleof the second adherent) for protecting the sensor chip 12 with securingentrance of light. In order to prevent degradation of the sensor chip 12caused by exposure to moisture, a first bonding surface 17 on theceramic package 11 is hermetically bonded to a second bonding surface 18on the window plate glass 16 via an epoxy type adhesive (an example ofthe adhesive) layer (adhesive layer) 24 thereby forming a sealingstructure 21 (circled area in FIG. 1).

As shown in FIG. 2, a monomolecular film 22 (an example of the film) ofthe first film-forming compound, which is bound to the surface of thefirst bonding surface 17 at one end of the molecule thereof and has anepoxy group (an example of the first functional group) for forming abond with a molecule of the epoxy type adhesive at the other end of themolecule, is formed on the surface of the first bonding surface 17 onthe edge of the ceramic package 11, a monomolecular film 23 (an exampleof the film) of the second film-forming compound, which is bound to thesurface of the second bonding surface 18 at one end of the moleculethereof and has an epoxy group (an example of the second functionalgroup) for bonding with a molecule of the epoxy type adhesive at theother end of the molecule, is formed on the second bonding surface 18 onthe edge of the window plate glass 16, the molecule of the adhesiveforming the adhesive layer 24 being bound to the epoxy groups of thefirst and second film-forming compounds.

The sealed structure 21 is formed by a bonding method including: step Aof bringing the first film-forming compound having at each end of onemolecule thereof an epoxy group and an alkoxysilyl group (an example ofthe first bonding group) into contact with the first bonding surface 17thereby binding the alkoxysilyl group to the hydroxy group 25 (anexample of the surface functional group) of the first bonding surface 17to selectively form the monomolecular film 22 of the first film-formingcompound on the first bonding surface 17 (see FIGS. 3(A) and 3(B)); stepB of bringing the second film-forming compound having at each end of themolecule thereof an epoxy group and an alkoxysilyl group (an example ofthe second bonding group) into contact with the second bonding surface18 thereby binding the alkoxysilyl group to the hydroxy group (anexample of the surface functional group) of the second bonding surface18 to selectively form the monomolecular film 23 of the secondfilm-forming compound on the second bonding surface 18 (see FIGS. 3(A)and 3(B)); and step C of bringing the first bonding surface 17 havingthe monomolecular film 22 of the first film-forming compound intocontact by pressure with the second bonding surface 18 having themonomolecular film 23 of the second film-forming compound while settingthe epoxy type adhesive to be in contact with the epoxy groups of thefirst and second film-forming compounds, thereby binding the epoxygroups of the first and second film-forming compounds to the molecule ofthe epoxy type adhesive forming the adhesive layer 24 (see FIG. 2).

The steps A to C are further described below in detail.

In the step A, the first bonding surface 17 on the edge of the ceramicpackage 11 is brought into contact with the first film-forming compoundhaving at the ends of the molecule thereof an epoxy group and analkoxysilyl group thereby binding the alkoxysilyl group to the hydroxygroup 25 on the first bonding surface 17 to selectively form themonomolecular film 22 of the first film-forming compound on the firstbonding surface (see FIGS. 3(A) and 3(B)).

The first film-forming compound having an epoxy group may be anycompound capable of adsorbing or adhering to the surface of the ceramicpackage 11 to form a monomolecular film through self-organization. Thecompound is preferably the alkoxysilane compound expressed by thegeneral formula (Chemical formula 1) having an epoxy group (oxiranering)-containing functional group at one end, and an alkoxysilyl groupat the other end of the linear alkylene group.

E-(CH₂)_(m)—Si(OR)₃  [Chemical formula 1]

In the above formula, E represents an epoxy group-containing functionalgroup, m represents an integer of 3 to 20, and R represents an alkylgroup having 1 to 4 carbon atoms.

Specific examples of the epoxy group-containing first film-formingcompound include the following alkoxysilane compounds (1) to (12).

(1) (CH₂OCH)CH₂O(CH₂)₃Si(OCH₃)₃

(2) (CH₂OCH)CH₂O(CH₂)₇Si(OCH₃)₃

(3) (CH₂OCH)CH₂O(CH₂)₁₁Si(OCH₃)₃

(4) (CH₂CHOCH(CH₂)₂)CH(CH₂)₂Si(OCH₃)₃

(5) (CH₂CHOCH(CH₂)₂)CH(CH₂)₄Si(OCH₃)₃

(6) (CH₂CHOCH(CH₂)₂)CH(CH₂)₆Si(OCH₃)₃

(7) (CH₂OCH)CH₂O(CH₂)₃Si(OC₂H₅)₃

(8) (CH₂OCH)CH₂O(CH₂)₇Si(OC₂H₅)₃

(9) (CH₂OCH)CH₂O(CH₂)₁₁Si(OC₂H)₃

(10) (CH₂CHOCH(CH)₂)₂CH(CH₂)₂Si(OC₂H₅)₃

(11) (CH₂CHOCH(CH)₂)₂CH(CH₂)₄Si(OC₂H₅)₃

(12) (CH₂CHOCH(CH)₂)₂CH(CH₂)₆Si(OC₂H₅)₃

In the above formulae, the (CH₂OCH)CH₂— group represents the functionalgroup (glycidyl group) expressed by Chemical formula 2, and the(CH₂CHOCH(CH₂)₂)CH— group represents the functional group(3,4-epoxycyclohexyl group) expressed by Chemical formula 3.

The monomolecular film 22 of the first film-forming compound is formedby applying a reaction mixture comprising an epoxy group-containingalkoxysilane compound, a condensation catalyst for accelerating thecondensation reaction between the alkoxysilyl group and the hydroxygroup 25 of the surface of the ceramic package 11 and a nonaqueousorganic solvent onto the first bonding surface 17 on the edge of theceramic package 11, and then allowing the reaction mixture to react inair at room temperature. The application may be carried out by, forexample, screen printing or ink jet printing.

Examples of the condensation catalyst include metal carboxylates,carboxylic acid ester metal salts, metal carboxylate polymers, metalcarboxylate chelates, and metal salts of titanate esters and titanateester chelates.

The content of the condensation catalyst is preferably from 0.2 to 5% bymass, more preferably from 0.5 to 1% by mass based on the alkoxysilanecompound.

Specific examples of the metal carboxylates include stannous acetate,dibutyltin dilaurate, dibutyltin dioctate, dibutyltin diacetate,dioctyltin dilaurate, dioctyltin dioctate, dioctyltin diacetate,stannous dioctanoate, lead naphthenate, cobalt naphthenate, and 2-ironethylhexenoate.

Specific examples the carboxylic acid ester metal salts includedioctyltin bisoctylthioglycolate and dioctyltin maleate.

Specific examples the metal carboxylate polymers include a dibutyltinmaleate polymer and a dimethyltin mercaptopropionate polymer.

Specific examples the metal carboxylate chelates include dibutyltinbisacetyl acetate and dioctyltin bisacetyl laurate.

Specific examples the titanate esters include tetrabutyl titanate andtetranonyl titanate.

Specific examples the titanate ester chelates includebis(acetylacetonyl)di-propyltitanate.

The alkoxysilyl group and the hydroxy group 25 of the surface or theceramic package 11 cause condensation reaction to form the monomolecularfilm 22 of the first film-forming compound having the epoxygroup-containing structure expressed by Chemical formula 4. The threesingle bonds extending from the oxygen atoms are each bound to thesurface of the ceramic package 11 or a silicon (Si) atom of an adjacentsilane compound, and at least one of the single bonds is bound to thesurface of the ceramic package 11 (for example, an aluminum atom on analumina package).

An alkoxysilyl group is decomposed in the presence of moisture, so thatits reaction is preferably carried out in air having a relative humidityof 45% or less. The condensation reaction is inhibited by oil, fat, andmoisture sticking to the surface of the ceramic package 11. Therefore,it is preferable that these impurities be removed in advance bythoroughly washing and drying the ceramic package 11.

When any of the above-described metal salts is used as the condensationcatalyst, the period required to complete the condensation reaction isabout 2 hours.

The reaction period can be reduced by about ½ to ⅔ by replacing themetal salt as the condensation catalyst with one or more compoundsselected from the group consisting of ketimine compounds, organic acids,aldimine compounds, enamine compounds, oxazolidine compounds, andaminoalkylalkoxysilane compounds.

Alternatively, the reaction period can be further reduced by using anyof the above compounds as a co-catalyst in combination with the metalsalt at a mass ratio of 1:9 to 9:1, preferably about 1:1.

For example, when the monomolecular film 22 of the first film-formingcompound is formed under the same conditions as described above, exceptthat H3 manufactured by Japan Epoxy Resins Co., Ltd., which is aketimine compound, is used as the condensation catalyst in place ofdibutyltin bisacetyl acetate, which is a metal carboxylate chelate, thereaction period is reduced to about 1 hour without loss of the qualityof the ceramic package 11.

The reaction period of the formation of the monomolecular film 22 of thefirst film-forming compound can be further reduced to about 20 minutesthrough the use of a mixture of H3 (manufactured by Japan Epoxy ResinsCo., Ltd.) and dibutyltin bisacetyl acetonate (mixing ratio is 1:1) asthe condensation catalyst, where the other conditions are the same asdescribed above.

The ketimine compounds which may be used herein are not particularlylimited, and examples thereof include 2,5,8-triaza-1,8-nonadiene,3,11-dimethyl-4,7,10-triaza-3,10-tridecadiene,2,10-dimethyl-3,6,9-triaza-2,9-undecadiene,2,4,12,14-tetramethyl-5,8,11-triaza-4,11-pentadecadiene,2,4,15,17-tetramethyl-5,8,11,14-tetraaza-4,14-octadecadiene,2,4,20,22-tetramethyl-5,12,19-triaza-4,19-trieicosadiene.

The organic acid which may be used herein are also not particularlylimited, and examples thereof include formic acid, acetic acid,propionic acid, butyric acid, and malonic acid.

Preparation of the reaction mixture may use organic chlorine solvents,hydrocarbon solvents, fluorocarbon solvents, silicone solvents, andmixture of these solvents. In order to prevent hydrolysis of thealkoxysilane compound, it is preferable that moisture be removed fromthe solvent used herein with a drying agent or through distillation. Theboiling point of the solvent is preferably from 50 to 250° C.

Specific examples of the solvent which may be used herein includenonaqueous petroleum naphtha, solvent naphtha, petroleum ether,petroleum benzene, isoparaffin, normal paraffin, decalin, industrialgasoline, nonane, decane, heating oil, dimethyl silicone, phenylsilicone, alkyl-modified silicone, polyether silicone, anddimethylformamide.

Other examples include alcohol solvents such as methanol, ethanol, andpropanol, and mixtures thereof.

Examples of the fluorocarbon solvents which may be used herein includechlorofluorocarbon solvents, FLUORINERT (manufactured by 3M UnitedStates) and AFLUID (manufactured by Asahi Glass Co., Ltd.). Thesesolvents may be used alone or in combination of two or more if they aremiscible with each other, and may be mixed with an organic chlorinesolvent such as dichloromethane or chloroform.

In the reaction mixture, the concentration of the alkoxysilane compoundis preferably from 0.5 to 3% by mass.

After completion of the reaction, the excessive alkoxysilane compoundand condensation catalyst remaining on the surface as unreacted residuesare washed off with a solvent thereby forming the monomolecular film 22of the first film-forming compound on the first bonding surface 17. FIG.3(B) shows a schematic view of the surface of the first bonding surface17 having thereon the monomolecular film 22 of the first film-formingcompound which has been formed as described above.

The washing solvent may be any solvent capable of dissolving thealkoxysilane compound, and for example, dichloromethane, chloroform, orN-methylpyrrolidone are preferred because these solvents areinexpensive, can dissolve the alkoxysilane well, and are easy to removeby air drying.

After completion of the reaction, if the surface is allowed to stand inair without washing with a solvent, the alkoxysilane compound remainingon the surface is partially hydrolyzed by moisture in air to form asilanol group, which causes condensation reaction with the alkoxysilylgroup. As a result of this, a very thin polymer film composed ofpolysiloxane is formed on the first bonding surface 17. The polymer filmis not wholly fixed to the first bonding surface 17 via covalent bonds,but is as reactive as the monomolecular film 22 of the firstfilm-forming compound due to its epoxy groups. Therefore, the subsequentmanufacturing process will not be markedly affected even if no washingis conducted.

The epoxy group-containing alkoxysilane compound used in the presentembodiment may be replaced with other alkoxysilane compound expressed bythe following general formula (Chemical formula 5) having an amino groupat one end of its linear alkylene group and an alkoxysilyl group at theother end:

H₂N—(CH₂)_(m)—Si(OR)₃  [Chemical formula 5]

wherein m represents an integer of 3 to 20, and R represents an alkylgroup having 1 to 4 carbon atoms.

Specific examples of the amino-group containing film-forming compoundinclude the following alkoxysilane compounds (21) to (28).

(21) H₂N(CH₂)₃Si(OCH₃)₃

(22) H₂N(CH₂)₅Si(OCH₃)₃

(23) H₂N(CH₂)₇Si(OCH₃)₃

(24) H₂N(CH₂)₉Si(OCH₃)₃

(25) H₂N(CH₂)₅Si(OC₂H₅)₃

(26) H₂N(CH₂)₅Si(OC₂H₅)₃

(27) H₂N(CH₂)₇Si(OC₂H₅)₃

(28) H₂N(CH₂)₉Si(OC₂H₅)₃

Among the condensation catalysts which may be included in the reactionmixture, compounds containing a tin (Sn) salt react with amino groups toform a precipitate, and thus cannot be used as the condensation catalystfor amino-group containing alkoxysilane compounds.

Therefore, when an amino-group containing alkoxysilane compound is used,the condensation catalyst may be a single compound or a mixture of twoor more of the compounds selected from those used for the epoxygroup-containing alkoxysilane compound, except for tin carboxylates,carboxylic acid ester tin salts, tin carboxylate polymers, and tincarboxylate chelates.

The type and combination of the co-catalyst which may be used herein,the type of the solvent, the concentrations of the alkoxysilanecompound, condensation catalyst, and co-catalyst, and the conditions andperiod of the reaction are the same as the case with the epoxygroup-containing alkoxysilane compound, so that explanations thereof areomitted.

Film-forming compounds such as alkoxysilyl group-containing pyrrolederivatives and imino group-containing imidazole derivatives are alsousable in the same manner as the amino-group containing film-formingcompounds. In addition, ketimine derivatives which form amino groupsthrough hydrolysis are also usable.

The ceramic package used as the first adherent in the present embodimentmay be replaced with a metal such as aluminum, glass, glass ceramic, ora synthetic resin such as an acrylic resin, a polycarbonate, or an epoxyresin.

When the first bonding surface has an active hydrogen group such as ahydroxy group or an amino group, the film-forming compound may be analkoxysilane compound as is the case with a ceramic package. When asynthetic resin is used as the adherent, an alkoxysilane compound may beused as the film-forming compound by grafting of a compound containingan active hydrogen group through corona discharge treatment or plasmatreatment.

(The Above is Related to Step A)

In the step B, the second film-forming compound having an epoxy groupand an alkoxysilyl group at each end of the molecule thereof is broughtinto contact with the second bonding surface 18 on the edge of thewindow plate glass 16, which is used as the window material of the imagesensor 10, thereby binding the alkoxysilyl group to the hydroxy group ofthe second bonding surface to selectively form the monomolecular film 23of the second film-forming compound on the second bonding surface 18(see FIGS. 3(A) and 3(B)).

The film-forming compound which may be used in the step B and thereaction conditions are the same as the case with the step A, so thatdetailed explanations thereof are omitted.

The window plate glass used in the present embodiment may be replacedwith a substrate of a transparent resin such as an acrylic orpolycarbonate resin whose bonding surface has been hydrophilizedthrough, for example, corona discharge treatment.

(The Above is Related to Step B)

In the step C, the first bonding surface 17 having the monomolecularfilm 22 of the first film-forming compound is brought into contact bypressure with to the second bonding surface 18 having the monomolecularfilm 23 of the second film-forming compound while setting the epoxy typeadhesive to be in contact with the epoxy groups of the first and secondfilm-forming compounds, thereby binding the epoxy groups of themonomolecular films 22 and 23 of the first and second film-formingcompounds to the molecule of the epoxy type adhesive forming theadhesive layer 24 (see FIG. 2).

For example, when the epoxy groups of the monomolecular films 22 and 23of the first and second film-forming compounds react with the aminogroups of the curing agent contained in the epoxy type adhesive to formbonds, the bond formation reaction is expressed by Chemical formula 6.In Chemical formula 6, R₁ and R₂ each independently represent a hydrogenatom, any alkyl group, aryl group, substituted alkyl group, orsubstituted aryl group.

The epoxy type adhesive which may be used for the formation of thesealed structure is not particularly limited, and may be any epoxy typeadhesive of one-component or two-component type, room temperature curingtype, or thermosetting type. The adhesive may be modified with, forexample, urethane or nitrile rubber.

Firstly, an epoxy type adhesive is applied on the monomolecular film 22of the first film-forming compound formed on the first bonding surface17 and/or the monomolecular film 23 of the second film-forming compoundformed on the second bonding surface 18. Application of the epoxy typeadhesive may be carried out by, for example, screen printing or ink jetprinting.

Secondly, the first bonding surface 17 having the monomolecular film 22of the first film-forming compound is brought into contact by pressurewith the second bonding surface 18 having the monomolecular film 23 ofthe second film-forming compound thereby binding the epoxy groups of themonomolecular films 22 and 23 of the first and second film-formingcompounds to the molecules of the epoxy type adhesive forming theadhesive layer 24 through curing reaction of the epoxy type adhesive.

The conditions for the curing reaction (for example, temperature andpressure) depend on, for example, the type of the epoxy type adhesiveand the sizes of the ceramic package 11 and the window plate glass 16.

An epoxy type adhesive may be used also in cases where the first andsecond film-forming compounds are amino-group containing film-formingcompounds, because the amino groups and epoxy groups of the epoxy typeadhesive form bonds through the reaction expressed by Chemical formula6.

The epoxy type adhesive used in the present embodiment may be replacedwith other reaction-curable adhesive such as an urethane adhesive.

During curing of the epoxy type adhesive at a high temperature, if thecoefficients of linear expansion of the first and second adherents aremarkedly different, internal stress may occur within the sealedstructure to cause its breakage due to the difference of the rates ofshrinkage during cooling. Therefore, the first and second adherents maybe heated to different temperatures using, for example, a heating block.In this case, it is preferable that the temperature of the first orsecond adherent having a higher coefficient of linear expansion be lowerthan the temperature of the other adherent having a lower coefficient oflinear expansion. The heating temperatures for the first and secondadherents may be adjusted on the basis of their sizes and coefficientsof linear expansion such that their deformation volumes are equal duringcooling.

In the present embodiment, a sealed structure and a sealing method aredescribed. It is a matter of course that the present invention is alsoapplicable to a bonded structure and a bonding method which are incommon with the sealed structure and sealing method in that thestructure is formed by bonding together the surfaces of adherents via anadhesive layer, and the method is for forming the structure.

In the present embodiment, an image sensor is illustrated as aninstance. The sealed structure according to the present invention isalso applicable to semiconductor devices sealed in packages, such asEPROMs, CPLDs (programmable logic devices), CdS cells, and photo-laserdiodes, and electronic components such as line sensors, liquid crystaldisplays (LCDs), plasma display panels (PDPs), electroluminescence (EL)displays, and field emission displays (FEDs).

EXAMPLES

Examples for confirming the effects of the present invention aredescribed below, but the present invention will not limited to theseexamples.

Example 1 Making of Image Sensor

(1) Formation of Monomolecular Films of Film-Forming Compounds (Steps Aand B)

A ceramic package equipped with an image sensor chip, the image sensorchip having thereon electrode pads that are wire bonded to leads, and awindow plate glass were prepared and respectively thoroughly washed anddried.

Thereafter, 0.99 parts by weight of 3-glycidyloxypropyltrimethoxysilane(Chemical formula 7, manufactured by Shin-Etsu Chemical Co., Ltd.) and0.01 parts by weight of dibutyltin bisacetyl acetonate (condensationcatalyst) were weighed and dissolved in 100 parts by weight ofhexamethyldisiloxane to make a reaction mixture.

The resultant reaction mixture was applied by screen printing onto thebonding surfaces of the ceramic package and window plate glass, andallowed to react for about 2 hours in air at room temperature (relativehumidity 45%). Thereafter, the excessive alkoxysilane compound anddibutyltin bisacetyl acetonate were removed through washing withchloroform to form monomolecular films (thickness: about 1 nm) of theepoxy group-containing film-forming compound on the entire bondingsurfaces. (see FIG. 3(B)).

The monomolecular films thus formed were very thin and had a thicknessof nanometer level, so that they did not impair the configuration of theceramic package and window plate glass. The films were then allowed tostand in air without washing, the solvent completely evaporated,3-glycidyloxypropyltrimethoxysilane in the reaction mixture reacted withmoisture in air, and thus a ceramic package and a window plate glasseach having on the bonding surface thereof a very thin siloxane polymerfilm containing covalently bonded reactive epoxy groups were obtained.The siloxane polymer film was slightly thicker than the monomolecularfilm, but almost equivalent to the monomolecular film in the bondingpower for the bonding surface and reactivity with the adhesive in thestep C.

(2) Formation of Sealed Structure (Step C)

An epoxy type adhesive (EP51AO, a two-component epoxy type adhesive forceramic adhesion, manufactured by Master Bond Inc.) was applied on thebonding surfaces of the ceramic package and window plate glass eachhaving thereon the monomolecular film of the epoxy group-containingfilm-forming compound which had been selectively formed, the bondingsurfaces were brought into contact with each other by pressure, andheated for 1 hour in a heating oven at 100 to 150° C., to seal the imagesensor (FIG. 1).

The epoxy groups of the monomolecular films of the film-forming compoundcovalently bonded to the bonding surfaces of the ceramic package andwindow plate glass reacted with the amino groups of the molecules of thecuring agent contained in the adhesive to form bonds, whereby themonomolecular films of the film-forming compound selectively andchemically bound to the bonding surfaces were bound to the adhesivelayer formed by curing of the adhesive (FIG. 2). As a result of this, animage sensor having markedly high hermetic sealing properties wasobtained.

Example 2 Making of Electroluminescence Display

(1) Formation of Monomolecular Film of Film-Forming Compound (Steps Aand B)

A glass substrate having an electroluminescence (EL) array, and a resinfilm for covering the back face were respectively thoroughly washed anddried. The edges of the resin film had been hydrophilized through coronadischarge treatment.

Thereafter, 0.99 parts by weight of 3-aminopropyltrimethoxysilane(Chemical formula 8, manufactured by Shin-Etsu Chemical Co., Ltd.) and0.01 parts by weight of acetic acid (condensation catalyst) were weighedand dissolved in 100 parts by weight of hexamethyldisiloxane to make areaction mixture.

H₂N—(CH₂)₃—Si(OCH₃)₃  [Chemical formula 8]

The resultant reaction mixture was applied by screen printing onto thebonding surfaces of the glass substrate and resin film, and allowed toreact for about 2 hours in air at room temperature (relative humidity45%) to form on the entire bonding surfaces thin polymer films(thickness: about 50 nm) of the film-forming compound having aminogroups bound to the substrates.

(2) Formation of Sealed Structure (Step C)

An epoxy type adhesive (EP51AO, a two-component epoxy type adhesive forceramic adhesion, manufactured by Master Bond Inc.) was applied to thebonding surfaces of the glass substrate and resin film each havingthereon the polymer film of the amino group-containing film-formingcompound which had been selectively formed, the bonding surfaces werebrought into contact with each other by pressure, and heated for 2 hoursin a heating oven at 70 to 90° C., whereby the EL array was sealedtherein.

The amino groups of the polymer films covalently bonded to the bondingsurfaces of the glass substrate and resin film reacted with the epoxygroups of the molecules of the adhesive to form bonds, whereby thepolymer films selectively and chemically bound to the bonding surfaceswere bound to the adhesive layer formed by curing of the adhesive. As aresult of this, an EL display having markedly high hermetic sealingproperties was obtained.

REFERENCE NUMERALS

-   -   10 image sensor    -   11 ceramic package    -   12 sensor chip    -   13 lead    -   14 electrode pad    -   15 electrically conductive wire    -   16 window plate glass    -   17 first bonding surface    -   18 second bonding surface    -   21 sealed structure    -   22 monomolecular film of first film-forming compound    -   23 monomolecular film of second film-forming compound    -   24 adhesive layer    -   25 hydroxy group

1-12. (canceled)
 13. A bonded structure comprising a first bondingsurface on a first adherent covalently bonded to a second bondingsurface on a second adherent via an adhesive layer, wherein: the firstbonding surface comprises a first film of a first film-forming compoundcomprising at a first end of the compound a first functional groupcovalently bonded to the adhesive layer, and at a second end of thecompound a first surface bonding group covalently bonded to the firstadherent; and the second bonding surface comprises a second film of asecond film-forming compound comprising at a first end of the compound asecond functional group covalently bonded to the adhesive layer, and ata second end of the compound a second surface bonding group covalentlybonded to the second adherent.
 14. The bonded structure of claim 13,wherein the first functional group is an amino group or an imino group;the second functional group is an amino group or an imino group, and theadhesive comprises an epoxy group.
 15. The bonded structure of claim 13,wherein the first surface bonding group is an alkoxysilyl group; and thesecond surface bonding group is an alkoxysilyl group.
 16. The bondedstructure of claim 13, wherein the first adherent is metal, ceramic,glass, or plastic; and the second adherent is metal, ceramic, glass, orplastic.
 17. The bonded structure of claim 13, wherein the first film isa monomolecular film, the second film is a monomolecular film, or boththe first and the second films are monomolecular films.
 18. A sealedstructure comprising a first bonding surface on a first adherenthermetically bonded to a second bonding surface on a second adherent viaan adhesive layer, wherein: the first bonding surface comprises a firstfilm of a first film-forming compound comprising at a first end of thecompound a first functional group covalently bonded to the adhesivelayer, and at a second end of the compound a first surface bonding groupcovalently bonded to the first adherent; and the second bonding surfacecomprises a second film of a second film-forming compound comprising ata first end of the compound a second functional group covalently bondedto the adhesive layer, and at a second end of the compound a secondsurface bonding group covalently bonded to the second adherent.
 19. Thesealed structure of claim 18, wherein the first adherent is metal,ceramic, glass, or plastic; and the second adherent is metal, ceramic,glass, or plastic.
 20. The sealed structure of claim 18, wherein thefirst film is a monomolecular film, the second film is a monomolecularfilm, or both the first and the second films are monomolecular films.21. The sealed structure of claim 18, wherein the first functional groupis an amino group or an imino group; the second functional group is anamino group or an imino group, and the adhesive comprises an epoxygroup.
 22. The sealed structure of claim 18, wherein the first surfacebonding group is an alkoxysilyl group; and the second surface bondinggroup is an alkoxysilyl group.
 23. An electronic component having thesealed structure of claim
 18. 24. The electronic component of claim 23,wherein the electronic component is a semiconductor device, an imagesensor, a line sensor, a liquid crystal display, a plasma display panel,or an electroluminescence display sealed in a package.
 25. An electroniccomponent having the bonded structure of claim
 13. 26. The electroniccomponent of claim 25, wherein the electronic component is asemiconductor device, an image sensor, a line sensor, a liquid crystaldisplay, a plasma display panel, or an electroluminescence displaysealed in a package.
 27. A bonding method comprising: bringing a firstfilm-forming compound comprising at a first end of the compound a firstfunctional group configured to form a covalent bond with an adhesive,and at a second end of the compound a first surface bonding group intocontact with a first bonding surface of a first adherent to covalentlybond the first surface bonding group to a surface functional group ofthe first bonding surface to form a film of the first film-formingcompound on the first bonding surface; bringing a second film-formingcompound comprising at a first end of the compound a second functionalgroup configured to form a covalent bond to the adhesive, and at asecond end of the compound a second surface bonding group into contactwith a second bonding surface of a second adherent to covalently bondthe second surface bonding group to a surface functional group of thesecond bonding surface to form a film of the second film-formingcompound on the second bonding surface; and bringing the first bondingsurface having a first film of the first film-forming compound intocontact by pressure with the second bonding surface having a second filmof the second film-forming compound while setting the adhesive to be incontact with the first and second functional groups, to bond the firstand second functional groups to the adhesive.
 28. The bonding method ofclaim 27, wherein the first functional group is an amino group or animino group; the second functional group is an amino group or an iminogroup, and the adhesive comprises an epoxy group.
 29. The bonding methodof claim 27, wherein the first surface bonding group is an alkoxysilylgroup; and the second surface bonding group is an alkoxysilyl group. 30.The bonding method of claim 27, wherein the first adherent has acoefficient of linear expansion that is greater than a coefficient oflinear expansion of the second adherent and during the contacting atemperature of the first adherent is lower than a temperature of thesecond adherent.
 31. The bonding method of claim 27, wherein the firstfilm is a monomolecular film, the second film is a monomolecular film,or both the first and the second films are monomolecular films.